Construction records made easy! Share field data to the cloud with AR heat maps

Table of Contents

• What is an AR heat map?

• Challenges of conventional construction records

• How AR heat maps change construction records

• Benefits of sharing field data to the cloud

• As-built management evolving with AR technology

• Simple surveying with LRTK

• Frequently Asked Questions

In recent years, digitalization on civil engineering and construction sites has accelerated, and the use of AR (augmented reality) technology is attracting attention. By using AR on construction sites, information that was difficult to grasp from drawings or numerical data alone can be intuitively visualized over the actual scene. A representative example of this is the “AR heat map” introduced here.

With an AR heat map, even subtle deviations in on-site construction results (as-built) can be detected without being overlooked, dramatically improving the efficiency of construction records and quality control. Also, data acquired on site can be shared immediately via the cloud, allowing the situation to be checked in real time from a remote office.

This trend of on-site DX (digitalization) aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, and AR heat maps are attracting attention as one of the cutting-edge technologies supporting it. This article explains how AR heat maps work and their benefits, and also introduces “LRTK,” an easy high-precision surveying tool that combines a smartphone with GNSS. If you are interested in on-site DX, please refer to this information.

What is an AR heat map?

An AR heat map visualizes deviations by comparing three-dimensional data (point clouds) obtained by measuring completed structures or ground with the design data, and representing the differences using colors. Specifically, the height-direction differences between post-construction point cloud data and the design model (or reference surface) are calculated, and areas with larger deviations are displayed in red or orange while smaller deviations are shown in green or blue. This allows you to instantly determine where on site the surface is built up higher than the design or where insufficient excavation has left areas lower than intended. On the heat map, areas finished higher than the design appear in red or orange, while areas matching the design appear in green or blue, enabling intuitive discrimination between good areas and areas with excesses or shortages by color.

Traditionally, construction accuracy could only be understood by comparing numerical measurement data; a major feature of the heat map is that it intuitively “visualizes” accuracy via the heat map. In addition, by displaying this heat map data as AR (augmented reality) over the camera view on a smartphone or tablet, it can be overlaid on the actual site for verification. By simply walking the site while viewing the colored heat map on the screen, you can immediately grasp whether the as-built work conforms to the design.

Challenges of conventional construction records

On civil engineering worksites, construction records and as-built management have traditionally relied on manual measurements and paper or photo records. However, these conventional methods have several issues. Representative problems include the following:

• Surveying work requires manpower and time: Manual measurements using tape measures or surveying instruments require multiple people and take enormous time and effort to measure wide areas. The larger the site, the more difficult it was to measure all locations sufficiently.

• Risk of overlooking areas with partial measurements: Hand measurements capture only heights or thicknesses at points, and cannot pick up fine undulations between measurement points. As a result, differences from the design in unmeasured areas might go unnoticed.

• Cumbersome photo records and document organization: Photographing during construction and creating record books are indispensable for as-built management, but sticking photos into paper ledgers or organizing data files is very time-consuming. On busy sites, photos may be missed or recording errors can occur, which can lead to troubles later.

• Difficulties in comparing with design drawings and reporting: Comparing measurement results with allowable values on design drawings and judging pass/fail often relied on on-site calculations or manual annotations on drawings. When there are many points, manual calculations cannot keep up, and including report preparation it becomes a large burden for site engineers.

As described above, conventional construction record methods have weaknesses such as “limited coverage,” “prone to human error,” and “time-consuming record organization,” becoming burdens and quality risks on site.

How AR heat maps change construction records

The new construction record method using AR heat maps has emerged to address these issues. The problems mentioned above are being solved by introducing AR heat maps as follows.

• Rapid 3D measurement of wide areas: Using laser scanners or a smartphone’s LiDAR function, one person can obtain detailed 3D point cloud data of the entire site in a short time. Wide areas that could not be measured manually can be covered at once, significantly reducing the time and personnel required for surveying. Also, steep slopes and high places where people cannot safely enter can be measured remotely, reducing dangerous tasks.

• Preventing oversights through surface-based comparisons: Heat maps created from point clouds enable pass/fail checks that capture the site as surfaces. By using 3D data measured everywhere, even slight height differences are emphasized by color, allowing detection of small unevenness that previously went unnoticed.

• Share and store data in the cloud: Measured point cloud data and generated heat maps can be uploaded to the cloud for centralized management. Even huge files that are difficult to attach to emails can be shared with stakeholders simply by sending a URL link. Digital records eliminate the need for paper documents or photo books, reducing the effort required to organize records.

• Anyone can intuitively check results: Heat maps on the cloud can be viewed in a 3D viewer from a PC web browser or tablet. No special software is required; supervisors or clients can understand on-site as-built data intuitively by just opening a URL. Moreover, by walking the site with a smartphone, the heat map is overlaid via AR on the camera view, so workers without surveying expertise can easily understand problematic areas on the spot.

• Immediate on-site rework: With AR heat maps, deviations identified on the heat map can be corrected immediately on site. For example, if part of the work is found to be overbuilt after construction, the smartphone screen shows the relevant area so workers can grasp the required amount to remove and start corrective work right away. The traditional step of analyzing data and then re-marking the site is no longer necessary, preventing rework.

By incorporating AR heat maps into workflows, construction record tasks become faster and more accurate, achieving both improved site quality and streamlined record-keeping. The acquired 3D data and heat maps are evolving from mere records into tools for real-time quality improvement.

Benefits of sharing field data to the cloud

Cloud-based sharing of field data supports the use of AR heat maps. Processes that once involved carrying data on USB drives or distributing many drawings can be dramatically streamlined by switching to cloud sharing. The main benefits are summarized below.

• Stakeholders can access the latest information anytime: If point cloud data and heat maps acquired on site are uploaded to the cloud, the latest data will always be available on the server. Remote branch offices or headquarters can access and review the data via the internet at any time, allowing timely understanding of site conditions without visiting the site.

• Remote inspections and meetings are possible: By sharing 3D data on the cloud, clients or supervisors can conduct inspections online without traveling to the site. The Ministry of Land, Infrastructure, Transport and Tourism is promoting remote on-site confirmation (“remote presence”), and cloud-shared point cloud data is expected to support such new inspection methods.

• No need for specialized software or high-performance PCs: Because data can be viewed in a web browser, recipients do not need to prepare special software or expensive workstations. From site personnel to management, sharing a URL lets everyone easily view the same 3D model on their devices.

• Accumulate digital records as assets: As-built data stored in the cloud remains a valuable information asset after project completion. Detailed 3D as-built conditions that cannot be preserved in paper records can be saved for future use in maintenance and renovation planning. Past site data can be retrieved when needed, forming a foundation for long-term DX promotion.

Furthermore, the acquired 3D point cloud data is useful for electronic delivery of as-built results and integration with BIM/CIM models. Delivering detailed point cloud models of completed structures as data allows highly accurate as-built records in completion documents. Accumulated 3D data can be used for future maintenance and renovation planning, remaining a valuable information asset after construction.

By combining cloud sharing, on-site record data becomes not just a “one-time report” but a real-time shared asset that lives on into the future. Compared to the conventional approach of waiting until the next day for measurement results, a new style of immediate checking and sharing right after measurement is becoming established on sites. Decision-making speed improves, and the overall construction cycle efficiency is dramatically enhanced.

As-built management evolving with AR technology

With the arrival of AR heat maps, the approach to as-built management (post-construction quality inspection and recording) is also changing dramatically. The heat map itself has evolved beyond a pass/fail record into an AR-based improvement tool that immediately indicates areas to be corrected when overlaid on the actual site. This turns as-built management from a mere after-the-fact record into a real-time quality control process during construction.

For example, previously when an area failed an as-built inspection, the responsible person had to locate it on drawings and mark the spot on site. With AR heat maps, the location and deviation amount of problem areas are apparent on the smartphone screen, so repairs can begin immediately after measurement. Because the whole team can view the same image, there is no discrepancy in understanding and corrections proceed smoothly.

Checking the finish on site as work progresses reduces the risk of later “rework” or “rollback.” A cycle of immediate feedback on as-built results is established, realizing both quality assurance and productivity improvement. AR technology is a key driver supporting the DX (digital transformation) of construction sites.

Simple surveying with LRTK

Finally, as a solution for anyone to easily perform the 3D surveying that underlies AR heat maps, we introduce “LRTK.” LRTK is a series of compact, high-precision GNSS receivers developed by a venture company originating from the Tokyo Institute of Technology. By attaching one to a smartphone or tablet, centimeter-level positioning (half-inch accuracy) can be achieved without specialized surveying equipment. Combined with the LiDAR scanner function built into the latest iPhones and iPads, a smartphone instantly becomes a high-precision 3D scanner.

Using LRTK, surveying tasks that once required multiple people can be easily performed by one person. For example, walking the site while scanning with a smartphone + LRTK can quickly acquire high-density point cloud data. The acquired data can be uploaded directly to the cloud, where heat map creation and sharing are completed automatically. Heavy tripods, cables, and specialized software are unnecessary, and anyone on site can operate it intuitively.

With the advent of such smartphone surveying devices, the entire workflow of “measure, analyze, and share” can be completed on site. There is no need to procure expensive dedicated equipment; leveraging a smartphone enables low-cost adoption. LRTK is already being introduced by many local governments and construction companies, with reported cases of significantly reduced surveying and inspection times. For example, in emergency topographic surveys after heavy rain disasters, the smartphone and LRTK alone enabled rapid situation assessment without deploying heavy machinery. Combining ease of use and high precision, LRTK is an ideal first-step solution for on-site DX. Take advantage of these latest tools to dramatically enhance on-site safety and productivity and take the first step toward smart construction.

Frequently Asked Questions

Q. What equipment is needed to use AR heat maps? A. Please prepare a smartphone or tablet and a high-precision GNSS receiver (e.g., LRTK). If you have a device with a LiDAR scanner, such as the latest iPhone or iPad, on-site 3D scanning becomes even easier. Install the dedicated app and set up an account for the cloud service, and anyone can immediately start measurements and data sharing with AR heat maps.

Q. Can it be used without specialist knowledge or special software? A. Yes. The system is designed to be usable without specialist knowledge. Measurement to heat map generation is processed automatically by the system, so users simply follow on-screen instructions. Viewing generated heat maps only requires opening a URL in a browser to check the 3D model, so complex CAD software is unnecessary. The system is simple enough for site workers to operate and understand intuitively. In practice, there are cases where workers used it successfully on their first try, so training burden is minimal.

Q. Is there any problem with the accuracy of measurement data or using it as an official record? A. The accuracy is comparable to conventional surveying instruments. RTK GNSS provides centimeter-level positioning (half-inch accuracy), ensuring the precision required for as-built management. Acquired point cloud data and heat maps can be used for rigorous comparisons with design drawings and pass/fail judgments, and may be submitted as official documentation for as-built proof. This method complies with the procedures of i-Construction (ICT construction) promoted by the Ministry of Land, Infrastructure, Transport and Tourism, so it can be used with confidence for official measurement records.

Q. Can it be used without an internet connection on site? A. Basic use is possible offline. First, perform positioning and point cloud acquisition on site with the smartphone and LRTK, and save the data on the device. Once you return to an area with a signal, upload to the cloud to share with stakeholders. Heat map data can also be downloaded to the device in advance so AR-based checks can be performed on site even without an internet connection.

Q. I am concerned about initial costs. Is there cost-effectiveness compared to traditional methods? A. AR heat maps using a smartphone and a compact receiver can reduce costs compared to newly purchasing large dedicated surveying equipment. With a small initial investment and greatly improved work efficiency that reduces personnel costs, cost-effectiveness is expected. Shorter surveying and inspection times per site increase productivity and lead to overall cost reductions. Once equipment and systems are in place, they can be reused across multiple projects, so long-term returns are likely.

Q. In what situations can AR heat maps be used? A. In civil works such as road construction and land development, they are effective for checking the as-built of embankments and cuttings. They can also be applied to a wide range of inspection items such as checking concrete thickness and height, and verifying the depth of buried pipes. AR heat maps are useful not only during construction but also for post-completion maintenance and disaster recovery records—any scenario where you want to compare and share site conditions in 3D.

Q. Can point cloud data obtained by drones or terrestrial laser scanners be used? A. Yes. LRTK’s cloud service allows uploading externally acquired point cloud data to create heat maps, so data from drone photogrammetry or terrestrial laser scanners (TLS) can be utilized as is. If the generated heat map is downloaded to a smartphone, it can be overlaid via AR and checked on site even without an LRTK receiver. It flexibly supports integration with existing surveying equipment and design data.

Q. Can heat maps be created if there is no design data for the site? A. Even without a reference design model or drawing data, it is possible to create a pseudo heat map based on the height distribution of the point cloud itself. For example, when only ground surface point clouds are available, color-coding the height distribution visualizes terrain undulations. However, for precise analysis of construction errors, it is preferable to prepare reference data such as design drawings or BIM models and generate difference heat maps against the point cloud.